Choke control for carburetor



April 26, 1966 T. M. BALL CHOKE CONTROL FOR CARBURETOR Original Filed Dec. 21, 1961 INVENTOR. 7'%@ 7714s M3477 United States Patent 3,248,094 CHOKE CONTROL FOR CARBURETOR Thomas M. Ball, Bloomfield Hills, 'Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Original application Dec. 21, 1961, Ser. No. 161,189.

Divided and this application Oct. 3, 1963, Ser. No 313,538

3 Claims. (Cl. 26139) sufliciently to cause the engine to stall, particularly during unfavorable weather conditions. It is accordingly another object :of the invention to provide improved simple and economical means which is highly effective to enable limited opening of the choke during starting only, so as to prevent stalling, and which allows normal choke operation after the engine has been started and the throttle has once been opened beyond the idle operating condition.

It is considered desirable to provide an automatic carburetor which will enable rapid engine starting merely by closing the starting motor circuit and without supplemental manual operation of the throttle. Such operation is often referred to as cam starting because the usual fast idle cam and cooperating thermostatic control are employed to maintain the throttle in the proper starting position. During cam starting the throttle will be at an idle position, such that the engine isespecially susceptible to -stalling in consequence of a sunge of cold inlet air immediately after being started.

Another object is therefore to provide improvedautomatic control means of the above character which is particularly adapted for cam starting, so as to limit the initial choke opening during starting only, without interfering with normal choke operation at other times.

Other objects of this'invention will appear in the following description and appended claims, reference being had to the accompanying-drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a fragmentary and generally schematic view of a carburetor embodying the present invention, portions being broken away to illustrate details of construction, the choke blade being shown in the starting position.

FIGURE 2 is a view similar to FIGURE 1, showing the choke blade in an idle operating position.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, an embodiment of the present invent-ion is illustrated by way of example comprising a carburetor for an automobile engine, the carburetor including a body having the customary air inlet induction conduit 11. An unbalanced choke blade or valve 12 is secured to a rotatable shaft 13 journalled at opposite ends in the body 10. The blade 12 is pivotal with shaft 3,248,094 Patented Apr. 26, 1966 13 and is located in the upper portion of conduit 11 in accordance with conventional practice. A throttle valve 14 secured to a rotatable shaft 15 journalled at opposite ends in the body 10 is provided at a downstream location of the conduit 11.

Suitably located within a portion of the engine so as to be responsive to an operating temperature thereof is a spiral bi-metallic thermostat spring 16 having a fixed end 17 secured to a fixed spindle 18. A swinging arm 19 pivotal on spindle 18 has an outer swinging end pivotally connected at 20 to the lower end of an operating link 21. A free end 22 of thermostat 16 is engaged with .arm 19 at the region of the connection 20 so as to urge arm 19 counterclockwise with progressively increasing force as the temperature decreases. The upper end of link 21 is pivotally connected at 23 to the swinging end of-a crank arm 24 keyed to the choke shaft 13.

Keyed to the throttle shaft 15 is a throttle control lever 25 having one swinging end pivotally connected at 26 with a personally actuated throttle link 27. The other end of lever 25 is provided with a threaded boss 28 having an adustable idle control screw or earn follower 29 screwed therein; The inner end of screw 29 is adapted to engage a stepped cam surface 30 of a fast idle cam 31 when the latter is in a predetermined cold idle operating position as described below. The cam 31 is keyed to a rotatable axial stub 32 journalled on the body 10 and is provided with a counterweight portion 33 effective to urge clockwise rotation of cam 31 by gravity force toward a. warm operating position.

Throttle lever 25 is normally urged clockwise toward the closed or idle position illustrated in FIGURES 1 and 2 by a customary throttle return spring 27a schematically illustrated under tension :between a projection 25a of lever 25 and a fixed portion 27b of the engine. Foot pedal actuation of shaft 27 is effectiveto swing lever 25 counterclockwise to open the throttle 14.

Upon closing movement of choke valve 12, the fast idle cam 31 is swung counterclockwise to the cold position by means of a link 34 having an upper end pivotally connected at 35 to a crank arm 36 keyed to shaft 13. The lower end of link 34 terminates in an extension 37 which projects in a direction parallel to the pivot axis of cam 31 through a lost motion slot 38 to complete a lost motion pivotal connection between link 34 and cam 31. Slot 38 is formed areuately within the counterweight portion 33 concentrically with the pivot axis of cam 31 to enable opening movement of choke valve 12 independently of movement of cam 31, as described below, by virtue of extension 37 riding within groove 38. Extending radially within cam 31 and intersecting slot 38 is a movement limiting notch 39 or de'tent slot arranged to receive extension 37 when cam 31 is in the cold position shown, FIGURE 1', thereby to limit opening movement :of choke valve 12. As is apparent, the link 34 is provided with a lost motion connection with cam 31 by reason of the extension 37, slot 38 and notch 39.

In order to render the position of choke valve 12 responsive to the pressure in conduit 11 downstream of throttle valve 14, a vacuum cylinder 40 formed integrally with body-10 contains a reciprocable piston 41 therein, pivotally connected at 42 to one end of a dog-leg link 43. The other end of the latter link is pivotally connected at 44 to the outer end of a projection 45 secured to valve 12 soas to swing the latter in a clockwise opening movement upon rightward movement of piston 41. The right end of cylinder 40 is connected by means of duct 46 with induction conduit 11 at a location downstream of throttle valve 14, FIGURE 2, thereby to urge opening of choke 12 against the-force of thermostat spring 16 when the pressure downstream of throttle valve 14 is low, i.e. during engine idling.

During operation .of the structure described, when screw 29 is in contact with the stepped cam surface 30, the frictional contact between screw 29 and surface 30 resulting from the tension of spring 27a is sufficient to prevent pivotal movement of cam 31 in consequence of the normal forces acting thereon, such as the forces resulting from counterweight 33, thermostat coil 16, piston 41, or the downwardly flowing air in conduit 11 acting on the unbalanced blade 12. In consequence, when the carburetor parts are in the cold position illustrated in FIGURE 1 and the cold engine is initially started, opening of the unbalanced choke blade 12 by the initial surge of cold inlet air in conduit 11 will be limited to a predetermined extent, as for example approximately by downward movement of extension 37 into notch 39.

During this starting operating, the throttle 14 will be maintained in a fast idle position by reason of screw 29 engaging the fast idle step of the cam surface 30, FIG- URE I. At the fast idle position, throttle 14 is cracked slightly open as illustrated in FIGURE 1, so that the engine will idle effectively in the cold condition. Thereafter, when throttle valve 14 is open from the fast idle position to accelerate the engine, the frictional engagement between screw 29 and cam surface 30 will be released to enable opening of choke valve 12 to the usual operating condition. By this time, the danger of engine stalling will have passed, because the stalling tendency described occurs only in the first two or three seconds of engine operation.

After the throttle 14 has been initially opened from the starting position of FIGURE 1 to enable opening of choke valve 12 to a running position, if the throttle 14 is then returned to a cold idle position so as to engage one of the lesser steps of .cam surface 30, the cam 31 will be locked against swinging movement as aforesaid by virtue of its frictional contact with screw 29. However in this instance, the cam 31 will now be in position to receive extension 37 within slot 38. Thus if the engineis allowed to run at idle for sufiicient time to relax the closing force of thermostat spring 16 as a result of warming of the engine, throttle'valve 12 will be free to open by virtue of movement of extension 37 along slot 38.

If the engine is operated in the warm condition under load and is then turned off and allowed to cool, choke valve 12 will be locked against return movement to the close-d position by contact between fast idle cam 31 and screw 29. Accordingly, in order to return the carburetor mechanism to the position illustrated in FIGURE 1, throttle 14 must first be opened to release the engagement between cam 31 and screw 29 thereby to enable thermostat spring 16 to return choke valve 12 and cam 31 to the position of FIGURE 1. Thereafter upon closing of throttle 14, screw 29 will engage the cold starting step of cam surface 30 as illustrated in FIGURE 1.

I claim:

1. In a fuel charging device for an internal combustion engine, air inlet conduit means, unbalanced choke valve means in said conduit means susceptible to being urged to an open position by the force of air flowing in said inlet conduit means, thermostatic means responsive to decreasing temperature for yieldingly closing said choke valve means, fast idle cam means pivotal between cold and warm positions, means yield-ingly urging said fast idle cam means toward its warm position, a throttle valve in said conduit means, idle control means movable with said throttle valve and engageable with said cam means at the cold position upon closing movement of said throttle valve to limit said closing movement to a slightly open fast idle position and also to prevent pivoting of said cam means until said throttle valve is opened from said fast idle position, means responsive to the pressure in said conduit means downstream of said throttle valve for yieldingly opening said choke valve means to an intermediate idle position against the tension of said thermostatic means when said throttle valve is opened from said fast idle position, and restricting means to restrict the initial opening of said choke valve means to prevent a sudden flow of inlet air in said conduit means sufiicient to stall said engine immediately after the latter has begun to operate under its own power with said cam means at said cold position and said throttle valve at said fast idle position and to enable opening of said choke valve means upon rotation of said cam means for said cold position to said inter- I mediate idle position, said restricting means comprising a link pivotally connected at one end with said choke valve means to move therewith, a lost motion slot extending in said cam means and having the other end of said link movably connected therein to ride therealong and to engage said oam means at one end of said slot and pivot said cam means to said cold position upon closing of said choke valve means, said slot at said one end thereof extending transversely to the direction of force applied through said link to its said other'end by force tending to open said choke valve means when said cam means is at said cold position, and a detent slot extending in said cam means in said direction and opening into said lost motion slot at said one end of the latter to receive said other link end and block movement thereof along said lost motion slot to limit opening of said choke motion slot extending in said cam means arcuately from said one end thereof and partially around the pivot axis of said cam means in the direction of rotation of said 'cam means from its cold to its warm position.

3. In the combination according to claim 2, said detent I slot extending radially inwardly from said lost motion slot at said one end of the latter.

References Cited by the Examiner UNITED STATES PATENTS 2,420,917 5/1947 Sutton et a]. 26l52 X 2,423,059 6/ 19471 Winkler. 2,762,354 9/ 1956 Winkler. 2,998,233 8/ 1961 Marsee.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner. 

1. IN A FUEL CHARGING DEVICE FOR AN INTERNAL COMBUSTION ENGINE, AIR INLET CONDUIT MEANS, UNBALANCED CHOKE VALVE MEANS IN SAID CONDUIT MEANS SUSCEPTIBLE TO BEING URGED TO AN OPEN POSITION BY THE FORCE OF AIR FLOWING IN SAID INLET CONDUIT MEANS, THERMOSTATIC MEANS RESPONSIVE TO DECREASING TEMPERATURE FOR YIELDINGLY CLOSING SAID CHOKE VALVE MEANS FAST IDLE CAM MEANS PIVOTAL BETWEEN COLD AND WARM POSITIONS, MEANS YIELDINGLY URGING SAID FAST IDLE CAM MEANS TOWARDS ITS WARM POSITION, A THROTTLE VALVE IN SAID CONDUIT MEANS, IDLE CONTROL MEANS MOVABLE WITH SAID THROTTLE VALVE AND ENGAGEABLE WITH SAID CAM MEANS AT THE COLD POSITIION UPON CLOSING MOVEMENT OF SAID THROTTLE VALVE TO LIMIT SAID CLOSING MOVEMENT TO A SLIGHTLY OPEN FAST IDLE POSITION AND ALSO TO PREVENT PIVOTING OF SAID CAM MEANS UNTIL SAID THROTTLE VALVE IS OPENED FROM SAID FAST IDLE POSITION, MEANS RESPONSIVE TO THE PRESSURE IN SAID CONDUIT MEANS DOWNSTREAM OF SAID THROTTLE VALVE FOR YIELDINGLY OPENING SAID CHOKE VALVE MEANS TO AN INTERMEDIATE IDLE POSITION AGAINST THE TENSION OF SAID THERMOSTATIC MEANS WHEN SAID THROTTLE VALVE IS OPENED FROM SAID FAST IDLE POSTION, AND RESTRICTING MEANS TO RESTRICT THE INITIAL OPENING OF SAID CHOKE VALVE MEANS TO PREVENT A SUDDEN FLOW OF INLET AIR IN SAID CONDUIT MEANS SUFFICIENT TO STALL SAID ENGINE IMMEDIATELY AFTER THE LATTER HAS BEGUN TO OPERATE UNDER ITS OWN POWER WITH SAID CAM MEANS AT SAID COLD POSITION AND SAID THROTTLE VALVE AT SAID FAST IDLE POSITION AND TO ENABLE OPENING OF SAID CHOKE VALVE MEANS UPON ROTATION OF SAID CAM MEANS FOR SAID COLD POSITION TO SAID INTERMEDIATE IDLE POSITION, SAID RESTRICTING MEANS COMPRISING A LINK PIVOTALLY CONNECTED AT ONE END WITH SAID CHOKE VALVE MEANS TO MOVE THEREWITH, A LOST MOTION SLOT EXTENDING IN SAID CAM MEANS AND HAVING THE OTHER END OF SAID LINK MOVABLY CONNECTED THEREIN TO RIDE THEREALONG AND TO ENGAGE SAID CAM AT ONE END OF SAID SLOT AND PIVOT SAID CAM MEANS TO SAID COLD POSITION UPON CLOSING OF SAID CHOKE VALVE MEANS, SAID SLOT AT SAID ONE END THEREOF EXTENDING TRANSVERSELY TO THE DIRECTION OF FORCE APPLIED THROUGH SAID LINK TO ITS SAID OTHER END BY FORCE TENDING TO OPEN SAID CHOKE VALVE MEANS WHEN SAID CAM MEANS IS AT SAID COLD POSITION, AND A DETENT SLOT EXTENDING IN SAID CAM MEANS IN SAID DIRECTION AND OPENING INTO SAID LOST MOTION SLOT AT SAID ONE END OF HE LATTER TO RECEIVE SAID OTHER LINK END AND BLOCK MOVEMENT THEREOF ALONG SAID LOST MOTION SLOT TO LIMIT OPENING OF SAID CHOKE VALVE MEANS SUFFICIENTLY TO PREVENT SAID SUDDEN FLOW WHEN SAID CAM MEAMS IS AT SAID COLD POSITION, SAID LOST MOTION SLOT AT SAID ONE END THEREOF BEING ALIGNED WITH SAID DIRECTION WHEN SAID CAM MEANS IS AT SAID INTERMEDIATE IDLE POSITION TO RECEIVE AND GUIDE SAID OTHER LINK END ALONG SAID MOVEMENT LIMITING SLOT IN THE DIRECTION FROM SAID ONE SLOT END UPON OPENING MOVEMENT OF SAID CHOKE VALVE MEANS INDEPENDENTLY OF MOVEMENT OF SAID CAM MEANS. 